Anfield was awash with ecstasy as goalkeeper Pepe Reina rushed the length of the field to join the celebrations with Ngog - a sign of what was riding on this result for Liverpool and manager Benitez.
Reds boss Benitez entered this crucial game with spirits lifted after managing director Christian Purslow added his weight to co-owner George Gillett's message that his future is not under threat.
But it was the commitment and energy shown by Liverpool in the face of four successive defeats that was always going to be the most realistic measure of the current circumstances surrounding Benitez.
And Liverpool delivered in emphatic fashion, backed by fervent Anfield supporters who recognised Benitez had reached a pivotal point in his five-year reign.
Liverpool held sway for most of a match that only occasionally touched the heights, but the workload of the respective keepers confirmed this was a victory well-earned by Benitez's side - and which now leaves them only four points behind the Premier League champions.
United mounted a late rally of sorts but Ngog's late goal gave the scoreline a more realistic appearance.
And watching it all after a late cameo as substitute was Michael Owen, returning to Anfield for the first time since joining United and being subjected to a venomous reaction from Liverpool's fans.
Owen was involved in the late drama as he was fouled by Jamie Carragher with United trailing 1-0 and boss Sir Alex Ferguson felt the Reds defender should have been shown a red card rather than yellow.
It was perhaps the stroke of luck Liverpool have been missing recently.
Events on the pitch, as ever, will ultimately dictate Benitez's fate and United fans arrived at Anfield in the mood to revel in Liverpool's current misfortune.
Phelan disappointed with result
Eric Cantona masks and a succession of banners served as a reminder that they now equal Liverpool's total of 18 league titles - with beach balls thrown on to the Anfield turf to mock the manner of Liverpool's defeat at Sunderland.
The Kop rallied behind Liverpool, who as expected were without injured captain Steven Gerrard, and they responded with an energetic first-half performance in which United keeper Van der Sar was fully extended.
Van der Sar leapt brilliantly to claw out Aurelio's free-kick in the 14th minute after Patrice Evra had been booked for his third foul in quick succession - even recovering to keep out Kuyt's effort from the rebound.
Kuyt was guilty of missing Liverpool's best chance of a frantic opening three minutes later when he failed to hit the target from the angle after he was released by Lucas.
Valencia's pace was posing real problems for Liverpool left-back Emiliano Insua, and he was the provider with a cross that saw Wayne Rooney's header clutched by Reina in front of an anxious Kop.
Liverpool were rising to the challenge of ending their recently dismal sequence, and Aurelio should have given them the lead 10 minutes before half-time, heading straight at Van der Sar from Yossi Benayoun's cross.
Benitez's side started well again after the break and Kuyt, his confidence perhaps sapped by earlier failures in front of goal, tried to set up Benayoun when the Netherlands striker would have been better served trying to test Van der Sar.
The goal Liverpool craved eventually came - and from a predictable source as Torres showed searing pace and clinical finishing to shrug off the attentions of Ferdinand before lashing a finish high past Van der Sar at The Kop end.
It was the signal for former Liverpool striker Owen to warm up, and he was subjected to a torrid reception and cries of "Judas" from the supporters who once idolised him.
Owen almost delivered the perfect answer to the taunts when he set up Valencia, but his shot smashed against the bar from a tight angle and United's last serious chance had gone.
There was still time for a frantic finish, with Vidic achieving the unenviable feat of a third red card in three games against Liverpool when he picked up a second yellow card for a foul on Kuyt. Mascherano joined him on the sidelines for a similar offence, this time a late challenge on Van der Sar - but the final word was left to Liverpool and youngster Ngog.
As United pressed forward in numbers, Liverpool broke and Ngog finished with composure from Lucas's pass to set the seal on a day that went almost perfectly to the script for besieged Benitez.